A method of preparing the salts of chiral, substituted cyclic β-aminoesters is described in U.S. Pat. No. 6,835,841. In this method, a cyclic β-enaminoester which is formally obtainable by reacting a cyclic β-ketoester with an amine is hydrogenated in the presence of a platinum catalyst under hydrogen pressure, while an acid, for example acetic acid, is added in an excess in relation to the hydrogenation substrate. The method described cannot readily be applied to the synthesis of chiral cyclic β-aminocarboxamides, particularly if the nitrogen of the enamine is substituted by a 1-phenylethyl group, for example. In this case, under the known conditions, hydrogenation of the aromatic ring also occurs, with the result that the hydrogenolytic cleaving of the chiral auxiliary to form the free β-aminocarboxamides becomes impossible.
The aim of the present invention is to provide a method for the direct preparation of cyclic β-aminocarboxamides with a high diastereoselectivity and yield.